The need for increased memory and processing capability continues to drive advances in central processing units (CPUs) and associated memory devices. A CPU typically includes a die, or microchips, which contain multiple processing units, communications hardware, and a local networking or communications bus. The core logic chipsets (cores) are the components that make up the processor die. The cores comprise the central processing logic of a computing system. A system's core logic typically includes a controller for handling memory functions, a cache for storing instructions, the logic for bus interfaces, and the functions of data paths. A single die can contain hundreds of processor cores. In increasing the number of cores, computer performance also increases, as does the need for more memory. For efficiency considerations, the memory-to-processor core ratio must stay relatively constant. That is, as more processors are added, memory must be proportionally added.
The need for higher memory to processor-core ratios is further driven by advances in virtualization. Virtualization makes it possible to run multiple operating systems and multiple applications on the same computer at the same time, increasing the utilization and flexibility of hardware. In one respect, virtualization allows the transformation of hardware into software, including the CPU, RAM, hard disk and network controller, to create a fully functional virtual machine that can run its own operating system and applications just like a physical computer. Virtualization is advantageous because it allows for server consolidation and increased processor accessibility. Thus, virtualization is driving the need for even higher memory to processor-core ratios, and higher memory capacity on servers.
The increased processing afforded by virtualization requires the addition of memory to maintain the required ratio. For speed considerations, the preferred way to add memory is to attach main memory directly to the processor. Performance is increased with data being stored directly in main memory, as opposed to slower, remote memory, e.g., memory on a disk. However, attaching memory directly to the processor typically imposes a limitation on the total amount of available memory. Attached memory may be inadequate for applications requiring larger memory capacities.
Memory compression is sometimes used to optimize available memory. Using compression, data may be encoded (represented as symbols) to take up less space. Memory compression effectively expands memory capacity up to two or more times for some applications without increasing actual physical memory and associated expenses. Despite its benefits, however, memory compression typically requires more memory bandwidth than is available in conventional attached memory, as well as compression logic.
Memory compression is often measured in terms of its associated compression ratio. The compression ratio is the quotient of memory space required by uncompressed data relative to the smaller amount of memory space required by compressed data. As data changes in main memory, the compression ratio can also change. When the compression ratio decreases, more physical memory is required. As a result, some physical memory must be vacated to accommodate changing data having a small compression ratio. This practice requires interaction with the operating system, taxing overall system processes. It can prove difficult to obtain the needed support from the operating systems to efficiently accomplish memory compression.
As discussed herein, many processors (and particularly, those having directly attached memory) are unequipped to perform memory compression. For instance, many such processors do not have adequate bandwidth or memory compression logic. The industry standard x86 processor is one example of a processor that does not support memory compression. As a result, users are relegated to finding alternative and less efficient ways to provide for more memory.
What is needed is a more efficient and cost effective way of providing additional memory bandwidth for systems using processors that do not support compression on memory directly attached to the processor.